Conventionally, a so-called autonomously traveling electric vacuum cleaner (cleaning robot) is known which detects an obstacle and the like using, for example, a sensor and the like while autonomously traveling on and cleaning a surface to be cleaned. Such an electric vacuum cleaner is provided with a main body case having a dust collecting portion and the like. The main body case has a lower portion with a suction port being formed so as to communicate with the dust collecting portion and with a pair of driving wheels being mounted so as to cause the main body case to travel autonomously. Additionally, inside the main body case, an electric blower is housed having a suction side communicating with the dust collecting portion. The electric blower is then driven to suck dust with air via the suction port into the dust collecting portion for cleaning.
In the case of such an electric vacuum cleaner, it is desirable to secure a suction force with the suction port close to the surface to be cleaned since the magnitude of a degree of vacuum changes at the suction port according to the magnitude of a gap between the suction port and the surface to be cleaned, while it is also required to prevent grip force from being lowered when the suction port is close to the surface to be cleaned causing a part of the suction port to drive over and be stuck in irregularities and the like protruding from the surface to be cleaned, thereby lifting the driving wheels from the surface to be cleaned.